1) Bending of an abnormally retarded 219 bp kinetoplast (Crithidia fasciculata) DNA fragment and all of its restriction enzyme digestion products predicted by computer modeling of the sequences was demonstrated by transverse polyacrylamide pore gradient gel electrophoresis. A 3-dimensional plot of [mobility vs gel concentration vs DNA length] separates bent DNA fragments from a surface pertaining to linear standards. 2) Mobilities of abnormally retarded DNA fragments (135 and 165 bp) from the upstream activator sequence of the rrnB-P1 promoter (E. coli) in transverse polyacrylamide pore gradient electrophoresis parallel those of linear standards. Computer modeling of these sequences and their restriction fragments reveals a central "knot" with bilateral wing-like curvature, not the monotonic curvature reported in section 1). This finding demonstrates the existence of two classes DNA fragments with abnormal retardation, one dependent, the other independent of gel concentration. 3) Transverse agarose pore gradient electrophoresis of four topoisomers of a 2.7 kb plasmid DNA obtained by treatment with topoisomerse I) exhibits an increase of apparent DNA length with gel concentration relative to linear standards, thus providing a test for DNA supercoiling. 4) Application of the Ogston model of electrophoretic migration through gels to DNA fragments allows one to interprete the concave plot of log(DNA mobility) vs gel concentration for DNA fragments up to 23 kb in length, in terms of a semihyperbolic decrease of the equivalent radius of the DNA molecule with uncrosslinked polyacrylamide concentration and a corresponding but shallower decrease of radius with agarose concentration, demonstrating and quantitating DNA deformation by gels. 5) Quantitative comparison of separation efficiency of four liquid sieving media for a range of particle radii up to 1,000 nm decrease from agarose to polyacrylamide to polyvinyl alcohol to methylhydroxypropylcellulose solutions. 6) Retardation of lambda DNA increases with the molecular, weight of uncrosslinked polyacrylamide (0.6 to 18 million). Since the range of retarding polymer concentrations also varies, the polymer of 5 million molecular weight presents the optimal sieving medium. 7) Epifluorescence microscopy of DNA, loaded as an agarose plug heated above the gelling temperature, demonstrates the migration of anagarose-DNA complex during electrophoresis in uncrosslinked polyacrylamide solution. 8) DNA electrophoresis in horizontal slab apparatus was developed, using an improved discontinuous buffer system. 9) Separation of DNA of 10 to 50 kb in length by capillary electrophoresis in polyacrylamide solution. 10) Computer simulation of molecular sieving as envisaged by the Ogston model in application to linear and bent particles in the size range of DNA.